Quasi-static Mechanics and Wave Propagation in Multistable Architected Materials
ME-EM Graduate Seminar Speaker Series
Dr. Julien Meaud
Georgia Institute of Technology
Abstract: Architected materials are materials whose properties arise from their architecture rather than from the intrinsic properties of the constituent materials. In recent years, it has been shown that architected materials that consist of a set of bistable unit cells (called multistable architected materials) have attractive properties, such as the ability to dissipate mechanical energy or to absorb mechanical energy. This presentation will focus on fundamental aspects of the quasi-static mechanics and dynamics of these types of architected materials for application as reconfigurable metamaterials, i.e. as materials whose properties can be tuned on demand. When a multistable system made of bistable unit cells is loaded in the quasi-static regime, the unit cells snap sequentially to their stable deformed configuration. If all unit cells are designed to be identical, this snapping sequence is unpredictable because it is affected by imperfections in the geometry, material properties and boundary conditions. The randomness of the snapping sequence would prevent these architected materials to be used as reconfigurable metamaterials. In our work, we have shown that tuning the local stiffness of the unit cells makes it possible to tune the snapping sequence. One possibility for tuning of the local stiffness is to introduce small variations in the values of the geometric parameters of the unit cells. More interestingly for practical applications, the snapping sequence can also be tuned dynamically after fabrication by varying the ambient temperature if the architected materials are made of multiple thermoviscoelastic polymers with different time-temperature properties. The mechanics of these systems is investigated using a theoretical model, finite element simulations and experiments with 3D printed samples. In addition to the analysis of the quasi-static mechanics of these systems, I will show numerical results for the propagation of elastic waves in multistable architected materials. I will demonstrate that these systems can be used as reconfigurable phononic materials that act as acoustic switches due to the presence of broadband tunable band gaps that can be adjusted by applying a deformation.
Bio: Professor Julien Meaud is an assistant professor in the Woodruff School of Mechanical Engineering at the Georgia Institute of Technology in Atlanta, GA. He received his Ph.D. from the University of Michigan, Ann Arbor in 2010 and conducted research on the biomechanics of the inner ear. After completing his Ph.D., he was a postdoc at the University of Michigan for a project on the mechanics of nanocomposites. His research group at Georgia Tech focused on research in hearing biomechanics (supported by NSF and NIH) and on the mechanics of architected materials and metamaterials.
Thursday, October 12, 2017 at 4:00 pm
Electrical Energy Resources Center (EERC), 103
1400 Townsend Drive, Houghton, MI 49931